40HP Big Twin will not start

[lark2004]

Re: 40HP Big Twin will not start

uh-oh, I bet the key had sheared off then. Can you see a slot on the side of the crankshaft? this is where the woodruff key sits, there is a slot in the tapered hole in the middle of the flywheel. If the key is sheared off, there will probably be a bit of it in each slot.

 

[jchrans]

Re: 40HP Big Twin will not start

I can see where there is a slot, and it appears to have something in it (the "KEY", I presume). Whatever it is is flush with the shaft.<br /><br />You say there will probably be a bit of it in each slot .. what other slot is there?

 

[Paul Moir]

Re: 40HP Big Twin will not start

Yeah, that's sheared off. I think lark2004 is thinking the rest of it is in the slot in the flywheel mating taper. This is certainly the cause of your bad spark.<br /><br />Follow CATransplant's instructions on cleaning up the taper in the link he gave you. That works 100% of the time. <br /><br />(To post a picture, you have to first host it on an independant picture hosting site like xs.to or tinypic.com. If you like, I can put them up for you. Just email them to paul.moir@ns.sympatico.ca )

 

[Paul Moir]

Re: 40HP Big Twin will not start

Ok, here's the pic:<br />

<br />

<br /><br />That's clearly sheared. Here's what they should look like:<br />

<br /><br />You can probably dig the old one out by tapping it with a hammer and small punch/nailset/nail/screwdriver you don't like. Evinrude.com says it's PN 307480. Any Johnson/Evinrude dealer should be able to get you one, but one that's been in the buisiness a while should have a bunch in stock.<br /><br />Clean up the taper and torque it down to 105ft/lbs (jam the starter with the largest peice of scrap plastic that will fit) and it won't do that again.<br /><br />PS - if the plate that the coils sit on is excessively wobbly, now's the time for Joe Reeves' wobbly armature plate fix:<br />Click here.<br /> <br />Otherwise it looks good under there.

 

[CATransplant]

Re: 40HP Big Twin will not start

Paul,<br /><br />I think there's an error in the parts list on those online sites. My records show that the key is 0302602. The other part number comes up as something else when you go to the dealer. She'd better take both part numbers. The key, OceanMist, looks like a half moon.

 

[CATransplant]

Re: 40HP Big Twin will not start

Paul,<br /><br />I think there's an error in the parts list on those online sites. My records show that the key is 0302602. The other part number comes up as something else when you go to the dealer. She'd better take both part numbers. The key, OceanMist, looks like a half moon.

 

[CATransplant]

Re: 40HP Big Twin will not start

OceanMist,<br /><br />The stuff under the flywheel looks just fine to me. I don't thing you'll need to replace any of it. Get that key and torque the flywheel down to 105 ft.-lb. and I'll be it fires right up.<br /><br />The exact same thing happened to me, and the outboard never ran better once I replaced the key. A simple fix.<br /><br />I think the last guy who worked on this just didn't properly torque down that big nut. That's what happened in my case.

 

[Paul Moir]

Re: 40HP Big Twin will not start

Oh yeah, actually 307480 seems to come up as a 5-pack of keys.

 

[jchrans]

Re: 40HP Big Twin will not start

You Gentlemen are completely and totally incredible and amazing! You have made something that I previously would have thought out of my league to be a simple operation... Mind you I haven't fixed the problem yet ... but you are just so wonderful with how fast and thoroughly you reply! I love you guys! I will order the part and will most likely be asking you again what to do because I do not know that torque is ... or how to measure it. And how do I know if the plate that the coils sits on is excessively wobbly.<br /><br />And for the record, since the manual is extremely vague on the subject ... why/how did you know this was a problem? I mean, what exactly is the purpose of the key and how does it's being sheared have the effect it does on the spark?\<br /><br />Again... I cannot thank you Gentlemen enough for sharing your knowledge and expertise ... you are gems!!!!

 

[jchrans]

Re: 40HP Big Twin will not start

Will I need 5 of them? Is this a regular occurance?

 

[CATransplant]

Re: 40HP Big Twin will not start

Well, I only bought three of the things. Now, I'll probably never use the other two. Shear pins, on the other hand....lots of rocks around here. I'm down to my last one. Time to visit the dealer again.

 

[Paul Moir]

Re: 40HP Big Twin will not start

The purpose of the key is to align the magnets in the flywheel and the opening of the points (little switches). It is not supposed to keep the flywheel from rotating but simply make it simple to install the flywheel. The pressure from torquing the flywheel nut keeps the flywheel from rotating. <br />Usually when it gets sheared, you completely loose spark but every once in a while the key will only half-shear or the magnets will end up near where they're supposed to be, resulting in a weak spark. Looks like that's what happened to you.<br /><br />CATransplant, take it from a cheap-skate - the shear pins are just 1/4" stainless rod cut 1 and 7/16" long. I use an old Big Twin shift-shaft. <br /><br />Oh, almost forgot - you torque the flywheel nut with a torque wrench. These tell you when you're pulling hard enough on them with a little indicator dial, pointer, or some of them click. 105 ft/lbs is a lot of force, similar to what you put on a car's lug-nuts.

 

[jchrans]

Re: 40HP Big Twin will not start

And what exactly do you mean when you say "Clean up the taper and torque it down to 105ft/lbs (jam the starter with the largest peice of scrap plastic that will fit) and it won't do that again"???

 

[Paul Moir]

Re: 40HP Big Twin will not start

I just mean to say to clean off any burrs or scrapes in the tapered part of the crankshaft and inside where the crankshaft and flywheel mate. If there's any protrusions, the flywheel is likely to slip and shear the key again.<br />Jaming the starter is a way of keeping the flywheel from turning when you torque the flywheel nut. Just raise up the starter's gear, and jam the gears with something relitively soft.

 

[jchrans]

Re: 40HP Big Twin will not start

You both are amazing Gentlemen! I cannot thank you enough for all your help! I will order the parts and buy the wrench that tells me how much torque I am applying when I put the flywheel back on. Should the flywheel go back on any way it fits, or is there something I should line it up with so it is in the right place?

 

[Paul Moir]

Re: 40HP Big Twin will not start

The flywheel key will line everything up for you. Just put the flywheel on the only way it fits.<br /><br />There's a fairly inexpensive torque wrench called a beam type. They actually pretty accurate but it can be hard to read the scale while your pulling on it. The other (inexpensive) type are the clickers. They're more expensive, and the cheap ones can be very inaccurate. But they have the advantage of giving an audible click when you reach the right tightness.

 

[jchrans]

Re: 40HP Big Twin will not start

Okay ... and while I have the flywheel off ... is there anything else I should replace (for good measure)? Although I have learned that with my luck (which is the equivelent of no luck ...) if it isn't broke ... DON'T FIX IT!

 

[Paul Moir]

Re: 40HP Big Twin will not start

Could be worse. Could be bad luck. <br /><br />Just that wobbly armature plate fix, if it's real bad. (it doesn't look that bad since the coils aren't hitting the flywheel) This basically involes denting up the brass plate under the coils and such.<br /><br />Could double check the gap on the points (they should open .020" maximum exactly). But frankly everything looks real clean & good in there. The ignition coils are one of the later designs so they must have been replaced recently. <br />You can find good info on tuning up those components over on Tom Travis' site:<br /> http://www.outboard-boat-motor-repair.com/ <br />His 5.5hp and 3hp use the same ignition system.

 

[CATransplant]

Re: 40HP Big Twin will not start

Since the engine was running fine before it sheared off the key, I doubt you need to do anything at all to the components under the flywheel. Check the points setting, as Paul recommends, but I wouldn't bother the armature plate. It didn't get worse overnight.<br /><br />Let us know how things turn out, and ask any questions you have while you're working on it. We'd like for you to have this fixed, once and for all, so you can get back on the water.

 

[Chinewalker]

Re: 40HP Big Twin will not start

To answer one of the previous questions, you SHOULDN'T need to replace the flywheel key often. It usually sheers when a previous servicing did NOT torque the flywheel properly. That torque is critical on thos Big Twins, as too much can crack the hub, and you've already found out what happens with too little....<br /><br />- Scott